Join nursing association, at heart it's private? (7)
I believe the answer is:
soldier
'private?' is the definition.
(I know that private is a type of private)
'join nursing association at heart' is the wordplay.
'join' becomes 'solder' (soldering is a kind of joining).
'nursing association' becomes 'i' (I can't justify this - if you can you should give a lot more credence to this answer).
'at heart' means one lot of letters goes inside another (inserted letters go to the heart of the word).
'solder' enclosing 'i' is 'SOLDIER'.
'it's' acts as a link.
Can you help me to learn more?
(Other definitions for soldier that I've seen before include "Military person" , "Eg, private" , "Warrior" , "One enlisted" , "Tommy Atkins or GI Joe?" .)